Non-Invasive Peripheral Arterial Evaluation: ABI with and without exercise
What is ankle brachial index (ABI) testing?
An ABI is performed by measuring blood pressures at a single level. Arterial pressures in the lower extremities at the ankle and toes are compared to the pressures measured in the arms. This is reported as a ratio and used as an indicator of the presence and severity of peripheral arterial disease (PAD).
What is peripheral arterial disease (PAD)?
PAD is a common circulatory problem affecting arteries where plaque, composed of cholesterol and scar tissue, accumulates along the inside wall of the artery causing narrowing of the flow lumen which reduces arterial blood flow to the limbs. Peripheral artery disease most commonly affects the lower extremities and the most common symptom of PAD are intermittent claudication or exercise induced calf, thigh and or buttock pain which abates with rest almost immediately. During exercise, muscles require more oxygen to function properly and the restriction of this delivery caused by PAD causes lactic acid to build up in the muscles leading to the cramps. The level of cramps depends on the level of the blockages in the arteries. Aortic or iliac artery blockages in the abdomen may cause buttock, thigh and calf cramps or claudication, whereas a thigh artery blockage (femoral artery) may only cause calf muscle cramps or claudication. Ankle brachial indices can not only identify the presence of PAD but help stratify the severity of the blockages. Checking ABIs at rest and after brief exercise on a treadmill following a very strict protocol may be helpful in identifying PAD in a patient who has mild enough disease to be missed by resting ABIs but which may be unmasked after increasing the muscle’s demand for oxygen with treadmill exercise. Making these determinations is not possible with MRI or CT scans, since they are not physiologic exams. The first diagnostic test that should be considered in a patient suspected to have PAD is the ABI with exercise.
What are the symptoms of PAD, and what are the indications that a peripheral arterial evaluation is needed?
Many patients may have a very mild degree of PAD and have little to no symptoms and probably will not have a reason to present for an evaluation. Approximately 8 million adults in the USA have symptomatic peripheral artery disease, and usually have symptoms of intermittent claudication(IC). As noted previously, muscle cramping occurs after periods of walking or exercising and resolve immediately after cessation of the activity. Symptoms should be very reproducible at approximately the same length of walking, regardless of the time of day , day of the week or other factors. This part of the patient history is important in establishing the clinical diagnosis of PAD. Diminished pulses may be noted in the feet of these patents although presence of pulses does not rule out PAD. In more severe cases of PAD, pain may occur at shorter distances of walking and at rest in bed when the legs are elevated, rest pain. Typically the pain in patients with rest pan is across the metatarsal bones (bones before the toes), and is relieved to some degree with hanging the legs over the bed. The color of the feet will also be a clue in that the feet will appear pale with elevation and beet red with dependency. The final and worse presentation of PAD is ischemic tissue loss , non healing wounds or gangrene. Ischemic ulcers can occur as a result of many injures or insults to the skin, and fail to heal because of critical reduction in arterial blood flow and oxygen/nutrient delivery to the tissues. These ulcers are usually very painful and the pain is rarely relieved by anything other than narcotics. Patients in this category constitute an emergency and should have immediate attention with physiologic testing and hospitalization for arteriography and planning of revascularization of the limb to preserve the limb. Symptoms or physical signs of PAD are listed below:
- Leg numbness or weakness
- Coldness in your lower leg or foot, especially when compared with the other leg
- Non-healing sores on your toes, feet or legs
- A change in the color of your legs (pale with elevation and ruby red with dependency)
- Hair loss or slower hair growth on your feet and legs
- Slower growth of your toenails
- No pulse or a weak pulse in your legs or feet
What can I expect during the exam?
A complete examination of both extremities takes approximately 30 minutes. It is performed in a private room lying on an exam table. A technologist will place blood pressure cuffs on the arms, legs, and toes to perform the blood pressures of the extremities. It may be necessary to have you walk on a treadmill slowly for no more than 5 minutes after the baseline pressures are taken to assess for any significant pressure changes after exercise. This is typically done to identify disease that may not be evident during the resting exam.
- Allow 30 minutes for a baseline exam. Allow 1 hour if exercise is required.
- No smoking for at least 1 hour before the exam.
- Shoes and socks will need to be removed for the pressure portion of the exam.
- Wear or bring comfortable walking shoes just in case exercise is required.
Please call us with any questions or to schedule an appointment for a Fort Myers Ankle Brachial Index test: (239) 694-8346